A magnet, like a compass needle, likes to point in a certain direction. But what if the material is layered, like a stack of pancakes? Scientists took just such a magnet made from a compound of chromium, germanium, and tellurium and set out to find out how stubbornly it resists having its magnetization turned.

To do this, they glued the sample onto a quartz tuning fork — a tiny pronged device that rings at a high frequency. When a magnetic field pulls the magnetization sideways, the tuning fork's vibration changes slightly. From that change, they could precisely measure the magnetic stiffness — the material's resistance to having its internal magnet rotated.

It turned out that at low temperatures, the magnet behaves like a flat two-dimensional sheet: its magnetization barely leaves the plane. When heated or subjected to a strong field, the picture changes — a sharp dip appears in the response curve as the magnetization reaches saturation. It's as if a stubborn door suddenly gives way when you push hard enough.

This method is like a stethoscope for magnetic materials. It hears internal stresses that ordinary magnetometers miss. And it has already helped distinguish spin-driven magnetism from orbital magnetism in another material — the superconductor CsV3Sb5. Now physicists have a reliable tool to listen to the "magnetic heartbeat" of thin films and layered crystals.